1. Field of the Invention
The present invention relates generally to the field of surgery, and more specifically, to an adjustable occipital plate which may be used in conjunction with a posterior rod system to fixate the occipital/cervical junction between the cranium and the spine.
2. Background of the Invention
Occipito-cervical fixation has been achieved using a variety of techniques which generally provide stabilization of the base of the skull with respect to the neck. In order to promote fusion, for example, bone struts formed of autogenous ribs or curved iliac crest struts have been fixed to the occiput and spinous processes, cervical laminae, or facets. Wires are used to fix the struts in place until bone fusion occurs.
The thickness of the occiput varies, however, and thus, the occiput is typically wired in regions of greater thickness such as near the foramen magnum, at the nuchal line, and along the midline crest. Holes are drilled in the occiput to receive the wires that are also fed through holes in the struts. Although bone fusion occurs with this technique, the struts may be weak prior to fusion, and additional orthosis is applied such as with a halo vest or other hard collar until the struts can provide acceptably strong immobilization. Alternatively, metal struts may be used.
Other techniques for occipito-cervical fixation involve the use of other metal implants. One metal implant is a stainless steel, U-shaped device known as a Steinman pin. The threaded pin is bent to match the contour of the occipito-cervical region, and fixed to the occiput and cervical laminae or facets using wires. The pin is generally symmetrically disposed about the spine, with the sides of the “U” creating a central region in which a bone graft can be disposed and further wired to the pin. When attached to the occiput and spine, the pin assumes an inverted-U configuration. Several holes are formed in the occiput so that the U-bend may be fixed in place.
Additional metal implants include grooved or roughened titanium rods, smooth steel rods in the form of a Hartshill rectangle or Ransford loop, a Cotrel-Dubousset rod screw plate, and titanium frames have been employed.